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curs_color(3X)									   curs_color(3X)

NAME
       start_color, init_pair, init_color, has_colors, can_change_color, color_content,
       pair_content, COLOR_PAIR - curses color manipulation routines

SYNOPSIS
       # include <curses.h>

       int start_color(void);
       int init_pair(short pair, short f, short b);
       int init_color(short color, short r, short g, short b);
       bool has_colors(void);
       bool can_change_color(void);
       int color_content(short color, short *r, short *g, short *b);
       int pair_content(short pair, short *f, short *b);

DESCRIPTION
   Overview
       curses support color attributes on terminals with that capability.  To use these  routines
       start_color  must be called, usually right after initscr.  Colors are always used in pairs
       (referred to as color-pairs).  A color-pair consists of a foreground  color  (for  charac-
       ters)  and a background color (for the blank field on which the characters are displayed).
       A programmer initializes a color-pair with the routine init_pair.  After it has been  ini-
       tialized,  COLOR_PAIR(n),  a  macro  defined in <curses.h>, can be used as a new video at-
       tribute.

       If a terminal is capable  of  redefining  colors,  the  programmer  can	use  the  routine
       init_color   to	 change   the  definition  of  a  color.   The	routines  has_colors  and
       can_change_color return TRUE or FALSE, depending on whether the terminal has  color  capa-
       bilities  and whether the programmer can change the colors.  The routine color_content al-
       lows a programmer to extract the amounts of red, green, and blue components in an initial-
       ized  color.   The routine pair_content allows a programmer to find out how a given color-
       pair is currently defined.

   Routine Descriptions
       The start_color routine requires no arguments.  It must be called if the programmer  wants
       to  use	colors,  and  before  any other color manipulation routine is called.  It is good
       practice to call this routine right after initscr.  start_color	initializes  eight  basic
       colors  (black,	red, green, yellow, blue, magenta, cyan, and white), and two global vari-
       ables, COLORS and COLOR_PAIRS (respectively defining the maximum number of colors and col-
       or-pairs  the  terminal	can support).  It also restores the colors on the terminal to the
       values they had when the terminal was just turned on.

       The init_pair routine changes the definition of a color-pair.  It takes	three  arguments:
       the  number  of	the  color-pair to be changed, the foreground color number, and the back-
       ground color number.  For portable applications:

       o   The value of the first argument must be between 1 and COLOR_PAIRS-1,  except  that  if
	   default  colors are used (see use_default_colors) the upper limit is adjusted to allow
	   for extra pairs which use a default color in foreground and/or background.

       o   The value of the second and third arguments must be between 0 and COLORS.  Color  pair
	   0  is  assumed  to be white on black, but is actually whatever the terminal implements
	   before color is initialized.  It cannot be modified by the application.

       If the color-pair was previously initialized, the screen is refreshed and all  occurrences
       of that color-pair are changed to the new definition.

       As an extension, ncurses allows you to set color pair 0 via the assume_default_colors rou-
       tine, or to specify the use of default colors (color number -1) if you  first  invoke  the
       use_default_colors routine.

       The  init_color	routine  changes the definition of a color.  It takes four arguments: the
       number of the color to be changed followed by three RGB values (for the	amounts  of  red,
       green,  and  blue components).  The value of the first argument must be between 0 and COL-
       ORS.  (See the section Colors for the default color index.)  Each of the last three  argu-
       ments  must  be	a  value between 0 and 1000.  When init_color is used, all occurrences of
       that color on the screen immediately change to the new definition.

       The has_colors routine requires no arguments.  It returns TRUE if the terminal can manipu-
       late colors; otherwise, it returns FALSE.  This routine facilitates writing terminal-inde-
       pendent programs.  For example, a programmer can use it to decide whether to use color  or
       some other video attribute.

       The  can_change_color routine requires no arguments.  It returns TRUE if the terminal sup-
       ports colors and can change their definitions; other, it returns FALSE.	This routine  fa-
       cilitates writing terminal-independent programs.

       The color_content routine gives programmers a way to find the intensity of the red, green,
       and blue (RGB) components in a color.  It requires four arguments: the color  number,  and
       three addresses of shorts for storing the information about the amounts of red, green, and
       blue components in the given color.  The value of the first argument must be between 0 and
       COLORS.	 The  values  that are stored at the addresses pointed to by the last three argu-
       ments are between 0 (no component) and 1000 (maximum amount of component).

       The pair_content routine allows programmers to find out what  colors  a	given  color-pair
       consists  of.   It  requires  three arguments: the color-pair number, and two addresses of
       shorts for storing the foreground and the background color  numbers.   The  value  of  the
       first argument must be between 1 and COLOR_PAIRS-1.  The values that are stored at the ad-
       dresses pointed to by the second and third arguments are between 0 and COLORS.

   Colors
       In <curses.h> the following macros are defined.	These are the default colors.  curses al-
       so assumes that COLOR_BLACK is the default background color for all terminals.

	     COLOR_BLACK
	     COLOR_RED
	     COLOR_GREEN
	     COLOR_YELLOW
	     COLOR_BLUE
	     COLOR_MAGENTA
	     COLOR_CYAN
	     COLOR_WHITE

RETURN VALUE
       The routines can_change_color() and has_colors() return TRUE or FALSE.

       All  other routines return the integer ERR upon failure and an OK (SVr4 specifies only "an
       integer value other than ERR") upon successful completion.

       X/Open defines no error conditions.  This implementation will return ERR  on  attempts  to
       use  color  values  outside  the range 0 to COLORS-1 (except for the default colors exten-
       sion), or use color pairs outside the range 0 to  COLOR_PAIRS-1.   Color  values  used  in
       init_color must be in the range 0 to 1000.  An error is returned from all functions if the
       terminal has not been initialized.  An error is returned from secondary functions such  as
       init_pair if start_color was not called.

	  init_color
	       returns	an error if the terminal does not support this feature, e.g., if the ini-
	       tialize_color capability is absent from the terminal description.

	  start_color
	       returns an error if the color table cannot be allocated.

NOTES
       In the ncurses implementation, there is a separate color activation flag,  color  palette,
       color  pairs  table,  and  associated  COLORS  and COLOR_PAIRS counts for each screen; the
       start_color function only affects the current screen.  The SVr4/XSI interface is not real-
       ly designed with this in mind, and historical implementations may use a single shared col-
       or palette.

       Note that setting an implicit background color via a color  pair  affects  only	character
       cells that a character write operation explicitly touches.  To change the background color
       used when parts	of  a  window  are  blanked  by  erasing  or  scrolling  operations,  see
       curs_bkgd(3X).

       Several caveats apply on 386 and 486 machines with VGA-compatible graphics:

       o   COLOR_YELLOW  is  actually  brown.	To get yellow, use COLOR_YELLOW combined with the
	   A_BOLD attribute.

       o   The A_BLINK attribute should in theory cause the background to go bright.  This  often
	   fails to work, and even some cards for which it mostly works (such as the Paradise and
	   compatibles) do the wrong thing when you try to set a bright "yellow" background  (you
	   get a blinking yellow foreground instead).

       o   Color RGB values are not settable.

PORTABILITY
       This implementation satisfies XSI Curses's minimum maximums for COLORS and COLOR_PAIRS.

       The  init_pair  routine accepts negative values of foreground and background color to sup-
       port the use_default_colors extension, but only if that routine has been first invoked.

       The assumption that COLOR_BLACK is the default background color for all terminals  can  be
       modified using the assume_default_colors extension.

       This  implementation  checks  the pointers, e.g., for the values returned by color_content
       and pair_content, and will treat those as optional parameters when null.

SEE ALSO
       curses(3X), curs_initscr(3X), curs_attr(3X), curs_variables(3X), default_colors(3X)

										   curs_color(3X)
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